The present invention relates to a ceramic-ceramic nanocomposite electrolyte having enhanced conductivity which may be used as an electrolyte in a solid oxide fuel cell.
The use of fuel cells has been widely increasing as fuel cells offer a clean, low pollution technology to provide electricity at high efficiencies. Of particular interest has been the use of solid electrolyte fuel cells which have demonstrated elevated energy production efficiency, high power density, and low levels of NOx and SOx emissions. Solid oxide fuel cells (SOFC) typically comprise two porous electrodes separated by a dense oxide ion-conducting electrolyte. Oxygen gas supplied at the cathode interacts with electrons to form oxygen ions which migrate through the electrolyte to the anode. However, solid oxide fuel cells suffer from a number of disadvantages including thermally induced stress resulting from their high operating temperature (1000° C.), cell fracture, and accelerated chemical interaction among components, which can lead to cell failure.
This is believed to be due to the fact that the electrolytes in current SOFCs typically comprise homogeneously doped stabilized zirconia, i.e., the cubic grains of stabilized zirconia are believed to be uniformly dispersed within grain boundaries which lowers the bulk conductivity of the electrolyte due to the lower conductivity of the grain boundaries. In addition, homogeneously doped stabilized zirconia must be heated to high temperatures (about 900-1000° C.) in order to exhibit significant oxygen ion conductivity useful for fuel cell applications.
In order to ensure the durability of the fuel cells and to reduce their operating temperature, the electrolytes used in the fuel cells must exhibit high conductivity, high mechanical strength, and high fracture toughness.
Accordingly, there is still a need in the art for an electrolyte for use in solid oxide fuel cells which provides high conductivity, lower operating temperatures, and good mechanical strength.